拜托解一下题!!!! 跪求啊~

(-2x-1)的2次方-4(x-1)(x+2)
(-2x-1)²-4(x-1)(x+2)
=(2x+1)²-4(x-1)(x+2)
=4x²+4x+1-4(x²+x-2)
=4x²+4x+1-4x²-4x+8
=9

化解:3a(2a的2次方-4a)-2a的2次方(3a+4)
3a(2a²-4a)-2a²(3a+4)
=6a²(a-2)-2a²(3a+4)
=2a²((3a-6)-(3a+4))
=2a²(3a-6-3a-4)
=2a²(-10)
=-20a²

(3x-5y)的2次方-(5y+3x)的2次方
(3x-5y)²-(5y+3x)²
=(3x-5y+5y+3x)(3x-5y-5y-3x)
=6x×(-10y)
=-60xy